The present invention relates to a method and an apparatus for providing the inner surface of pipe lines such as those made of steel or the like metal, concrete pipes or rigid resinous pipes, with a flexible tubular lining material through a liquid resin under pressure. More particularly, the present invention relates to a method and an apparatus for providing the inner surface of pipe lines, chiefly those already constructed, for example, underground pipe lines such as gas conduits, city water pipes and pipes enclosing power transmission wires or telephone cables, with a lining to reinforce the pipe lines or to repair damaged portions thereof.
It is well known that when underground pipe lines for gas or water are superannuated or damaged, gas or water leaks out causing many troubles and that deteriorated pipe lines or casings enclosing power transmission wires or telephone cables result in accidents caused by electric leakage or crosstalk. A countermeasure from the past to prevent such troubles is that when such underground pipe lines are superannuated, the pipe lines are dug up over the length of several ten to several hundred meters and replaced with new ones. In this case, however, supply of city water or gas has to be discontinued for a long period of time until the pipe replacing task has been finished. In case superannuated pipes are buried under public roads, people encounter much trouble and inconvenience since traffic on the roads is limited during the work for digging up such superannuated pipes and replacing them with new ones. Further, much labor and cost are required for renewing the pipes in addition to difficulty in the work itself for pipe exchange. Once more, it is not unusual that many of the known methods for renewing the deteriorated or damaged pipes cannot be utilized, due to the particular situations of the place where such pipes are buried. Thus, there is a great demand for the development of a new method for repairing and/or reinforcing pipes, especially those buried in the ground without necessitating difficult measures, for example, digging up the buried pipes.
In recent years, a strong probability of a big earthquake has been reported in many places in the world with the development of an earthquake predicting technique and consideration is being given to reinforcing underground pipes regardless of whether such pipes are superannuated or not to protect them from damage by earthquake. A method wherein a flexible plastic tube is inserted into underground pipes and bonded to the inner surface thereof is newly proposed for attaining both purposes of repairing damaged portions of the pipes and reinforcing the pipes so as to withstand mechanical shock by earthquake. In such a method, however, the step for inserting the flexible tube into the underground pipes is extremely difficult so that the work is almost impossible to execute in such places where the pipes are long or are curved in several portions.
Under such circumstances, a new method for providing pipes with a lining material with evagination wherein a flexible tube is inserted into a pipe while turning the tube inside out by the action of a pressurized fluid such as compressed air and bonded at the same time onto the inner surface of the pipe by the aid of a binder, was developed and has particularly been watched with interest in recent years. This method is advantageous in that insertion of a lining material into a pipe is easy and requires only a short period of time; the lining material is easily bonded onto the inner surface of the pipe; the treatment is applicable to pipes of a large or small diameter; and the process is operable even in the case when the pipe is curved in several portions. The method of this type is disclosed in U.S. Pat. Nos. 2,794,758, 3,132,062, 3,230,129 and 3,494,813 and British Pat. Nos. 1,025,011, 1,069,623 and 1,002,131.
British Pat. No. 1,002,131 relates to a method and device for evaginating a flexible tube but fails to give any description or suggestion on insertion of the tube into a pipe. British Pat. No. 1,025,011 discloses the means for inserting a tube into a pipe while turning the tube inside out. In this patent, however, the tube is not bonded only to the inner surface of the pipe and no technique is disclosed for this purpose. In U.S. Pat. Nos. 2,794,758, 3,132,062 and 3,494,813 and British Pat. No. 1,069,623 there is disclosed respectively a method for inserting a tube into a pipe while turning the tube inside out and bonding the tube onto the inner surface of the pipe. However, all of these known arts disclosed in these patents require previous application of a binder onto the inner surface of a pipe or tube prior to insertion of the tube. In case a tube is bonded as a lining to a pipe, an ordinary binder containing a volatile component cannot be used for the reason that both pipe and tube should be impervious. In such a method, therefore, the use of only a binder of such type that it contains no volatile component and the resinous component is curable with the lapse of time comes into question. When a binder is previously applied onto the inner surface of a pipe or tube, a considerably longer period of time is required until the binder is prepared and completely applied onto the inner surface, so that curing of the binder already starts prior to the insertion of the tube into the pipe, thus resulting in insufficient adhesion of the lining onto the inner surface of the pipe. The use of a binder having an extended pot life is thus required to prevent such premature curing but the time necessary for complete curing of the binder after the insertion treatment of the tube becomes invariably long.
U.S. Pat. No. 3,230,129 discloses a method wherein the inside of a pipe is charged with a binder and a tube is inserted into the pipe from one end thereof while turning the tube inside out and pushing the binder forward thereby bonding the evaginated portion of the tube onto the inner surface of the pipe by the aid of the binder remaining on the inner surface. However, this method has also a number of drawbacks. First of all, the quantity and distribution of the binder cannot be controlled at all so that the binder is almost absent in some areas between the pipe and the tube but is present in some areas in an extremely large amount between the pipe and the tube which is sufficient to make the path of gas or water locally narrower. Secondly, the binder must be used in an amount larger than that needed for bonding the tube to the pipe because the tube is allowed to proceed with simultaneous evagination within the pipe while pushing the binder forward. An excess amount of the binder in this case is, after all, discarded. Thirdly, when the pipe is inclined, for example, in such manner that the entrance of the tube is lower, the head pressure of the binder acts on the top or turning point of the proceeding tube where evagination occurs, so that the pressure required for evagination of the tube is fluctuated and the amount of the binder interposed between the pipe and the tube tends to vary.
Therefore, none of the prior art methods succeeded in providing pipes, especially those buried in the ground, with a lining according to a simple operation conducted in situ without moving or disjointing the pipes. In these circumstances, there is a great demand for development of a new method which entirely overcomes these drawbacks.